Crystallization and preliminary X-ray crystallographic analysis of a bacterial Asn-transamidosome.

Most canonical aminoacyl-tRNAs are synthesized directly by their cognate aminoacyl-tRNA synthetases (aaRSs), but glutaminyl-tRNA(Gln) and asparaginyl-tRNA(Asn) are synthesized indirectly by two-step processes. These processes are catalyzed by the transamidosome, a large ribonucleoprotein particle composed of GatA, GatB, GatC, aaRS and tRNA. In this study, the Asn-transamidosome from Pseudomonas aeruginosa was reconstructed and crystallized by mixing purified GatCAB complex, AspRS and tRNA(Asn). The crystal of the Asn-transamidosome belonged to space group P2₁, with unit-cell parameters a=93.3, b=186.0, c=287.8 Å, β=93.3°, and diffracted to 3.73 Å resolution. Preliminary X-ray crystallographic analysis showed that the asymmetric unit contained two Asn-transamidosomes, each composed of two GatCABs, one AspRS dimer and two tRNAAsns, indicating that the construction of the current Asn-transamidosome differs from that of Thermus thermophilus.